With all the USB devices I've done, you HAVE TO INSTALL THE SOFTWARE FIRST!
I'm afraid you have corruption in the Registry in that device area. Uninstall the Tascam stuff, unplug the unit. Since you are fresh with the XP, I suggest you delete the partition with a boot floppy using fdisk. (Do not format first.) Re-install your XP over again; get it running perfectly the way it should be with updates, SP2, etc.
Then install the Tascam software, (which should set up the drivers). Reboot. When you hit your desktop, now plug in the unit. It should setup trouble free.